Mitch Larkin crowned a hugely successful meet by posting the best time in the world this year in the 200m backstroke, as the Tokyo leg of the FINA/airweave Swimming World Cup drew to a close on Thursday.

But Larkin was denied a hat-trick of golds -- having won the 100m backstroke on Wednesday -- when David Plummer (USA) won the tightest of finishes in the 50m backstroke.

In the 200m, Larkin took charge from the outset, taking an average of almost 0.8 out of closest pursuer Ryosuke Irie (CLB/JPN) at each of the first three splits, before touching home in 1:53.34, ahead of Irie, who clocked 1:56.00.

"Like I said last night, I didn't quite expect that time," said Larkin, who had beaten his expectations by about 0.5 in the 100m.

"For me, today the question really was about endurance. I swam my way through the first 100 pretty comfortably and tried to keep my legs fresh."

Mitch Larkin (AUS) ©Japan Swimming Federation

The 30-year-old Plummer threw down the gauntlet in 50m qualifying with a 24.62, almost a second quicker than Larkin, eight years his junior.

The challenge was picked up by Larkin, who matched that time in the final, only to see Plummer grab the honours in 24.58.

"This morning was a bit average, I didn't handle the start and I was a bit flat," said Larkin.

"Tonight, I was really happy with that. The 50's a non-Olympic event so I don't really focus on it too much, but it's obviously important having a bit of speed for the 100."

Larkin said he couldn't split the 100m and 200m backstroke as to which gave him the best chance of gold at the Rio Olympics next year, but knows he's a marked man with his recent displays here and at the World Championships in Kazan, where he struck gold in both those events.

"For me the biggest difference is that I'll be hunted," he said.

"Coming off the worlds I've had people targeting me as a front runner. I'll make sure the boxes are ticked and keep doing what I'm doing, but it's a different challenge at the Olympics."

Larkin and compatriot Emily Seebohm (AUS) had visited temples in Tokyo on Tuesday, and joked at that day's official press conference how they had drawn out fortune papers that indicated both were about to suffer bad luck.

But Emily Seebohm (AUS) made it a hat-trick of golds at the Tatsumi International Swimming Center with victory in the 100m backstroke, meaning the duo defied the temple hoodoo in collecting five golds and a silver from their six events.

Emily Seebohm (AUS) ©Japan Swimming Federation

The Australian won both battles with Katinka Hosszu (HUN) on Wednesday, claiming gold in the 50m and 200m backstroke, and the Hungarian was second best in the 100m backstroke, as Seebohm drew clear.

"I couldn't let Mitch outdo me, I have a thing about beating boys!," said Seebohm, who clocked 58.37.

She's focusing on the 100m and 200m backstroke in particular for Rio 2016.

"I think my 100 and 200 are really strong, if I can keep doing that I'll be really happy. Doing times like that really helps, there are not many chances in Australia where you can race against the best in the world, so it's nice to be doing that so often out here."

Hosszu cut her second-day schedule to four events from six, which paid off, as in addition to claiming silver behind Seebohm, she struck gold in the 400m freestyle and 400m individual medley, and collected bronze in the night's opening event, the 100m freestyle.

"Today was a bit of an easier schedule for me, better spaces between my events, and so it made it a bit easier, but I feel I got tougher these two days," said Hosszu, known as the Iron Lady.

She has won the overall FINA World Cup series for the past three years, and is well clear in this year's standings with just the Doha and Dubai legs to come in November.

"I don't want to celebrate yet. I know I have quite a lot of points so I probably will be thinking about that title at the last leg in Dubai," she added.

Hosszu, who owns five world records, swam 10 events in Tokyo, claiming four golds amongst her eight medals. She has yet to be beaten in the 400m individual medley in this year's FINA/airweave World Cup series.

But the closest Hosszu has come to winning an Olympic medal at the past three Games was a fourth place at London 2012.

"I don't feel like Rio will be the end of my career. Of course I want to win an Olympic medal, but since I'm not obsessed with winning medals, I'm able to push myself and enjoy myself a lot more than before," she said.

Hosszu will be 31 when the 2020 Olympics come to Tokyo, but she's not ruling out an appearance.

"I certainly feel like I can be there for maybe one or two races, like the 100 backstroke. We have to see how the younger generation comes along, but if I can still get on the national team, then I want to be there."

Molly Hannis (USA) doubled up her gold tally. Having won the 100m breaststroke the previous night, she clocked 30.63 in the 50m breaststroke.

But it could have been so different if race leader Alia Atkinson (JAM) hadn't lost her action in the crucial last couple of strokes.

"I thought, 'I don't know if i can do it in this stroke, should I do another stroke'?," said Atkinson, who last December became the first black woman to win a world swimming title when claiming the 100m breaststroke at the World Championships in Doha.

That success has seen her thrust into the media spotlight, which has brought "more pressure, because there are more people looking at me to see what I accomplish," said the 26-year-old.

"But I've never had that before, so it's something that's giving me more confidence, and means my perseverance and dedication through the highs and lows is finally paying off."

The men's FINA/airweave World Cup series points leader, Cameron Van der Burgh (RSA), made it two golds from two finals, adding the 100m breaststroke -- in which he is the Olympic champion -- to Wednesday's 50m breaststroke triumph.

The 27-year-old is targeting the defence of his Olympic title at Rio 2016

"It's potentially the last Olympics for me at which I'll be fully competitive," he said. "Obviously I'm getting a little bit older now. so I'm going to put everything into this year. My times are very good, and it's the best I've ever done in a season."

Teen ace and home-crowd favourite Rikako Ikee (CLB/JPN) added the 100m freestyle and 50m butterfly to her 100m butterfly from the previous night.

Gold to Rikako Ikee (CLB/JPN) ©Japan Swimming Federation

The 15-year-old led home Miki Uchida (CLB/JPN) and Hosszu in the 100m freestyle, then set a world junior record of 26.17 in the 50m butterfly.

This year, the FINA/airweave World Cup series is being held in long-course pools for the first time since its inception in 1988.